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    3. Acoustic Analysis with COMET FEA VIBRATION ANALYSIS Generate structural model Run FEA program Compute surface velocities

    6. Concern Determination of sub-system (panel) contribution to the noise Use panel acoustic contribution analysis Associates the vibration of a panel to noise Transfer function Identify the type of contribution Negative, Positive, Neutral Make design changes

    7. Physical Interpretation

    9. Experimental Data Numerical determination of vibration data is limited to less than 200 Hz Use of experimental data allows the analysis to be carried at higher frequencies - 600 Hz COMET allows import of experimental data Used successfully by a major automobile company Sport utility vehicle Weight reduction of 10 lb. Reduction in sound level of 2 dB Development of vehicle for Asian-Pacific region Weight reduction of 1.3 lb. Sound level reduction of 6 dB

    10. Summary Identification of solutions not intuitively obvious PACA provides a systematic process for noise reduction Can be combined with experimental data Numerical determination of vibration data is limited to less than 200 Hz Use of experimental data allows the analysis to be performed at higher frequencies - 600 Hz COMET allows import of experimental data Used successfully by a major automobile manufacturer

    12. Porous Media Material utilizes multiple phenomena to minimize reflected or transmitted sound energy solid phase (the structure of the material) fluid phase (the fluid fills the holes) interactive between the above Primarily used to dissipate energy damping (viscous, structural, thermal) Examples of porous materials Glass fiber, Mineral wool, Partially open or open cells foams Typical applications Mufflers and ducts Vehicle sound insulation Aerospace structure sound insulation Seals

    13. Foam sandwiched by aluminum panel and air on both sides Boundary condition free panel edge condition impedance + velocity on one end impedance on the other end impedance = Double Panel TL

    14. Double Panel TL Unbounded connection between foam and aluminum panel Good correlation between theoretical (infinite plate) and SAFE results Infinite plate theory applicable

    15. Effect of Bond One of the plates is bonded to foam Poor correlation between theoretical (infinite plate) and SAFE results Good correlation between SAFE and experimental results Usage of glue increases stiffness - increase in TL

    16. Summary Models Sound Propagation Poroelastic, fluid, structural and solid domains Coupled and Uncoupled 2D, 3D, Axi-symmetric Frequency response, Modal Analysis Provides a powerful tool for the design of optimal modern noise control treatments Used in headliners, seats, carpets, trim lining, panel damping, aircraft skin insulation, wall insulation, enclosure liners, etc.

    18. Concern Objective Perform many design iterations by rapidly determining acoustic characteristics Analysis Aim Associate a single parameter with each design Computational Procedure Vibrational characteristic from FEA, Test, NAH Acoustic analysis using enhanced Rayleigh method Important Criteria Not actual sound level Variation of sound level from one design to another

    19. Analysis Process Identify the frequency range of interest Compute structural modes Select number of frequencies in the vicinity of the structural mode For each frequency Get surface velocity from structural analysis Compute sound power Enhanced Rayleigh Method

    20. Design Iteration Compute sound power for the mode Add sound power for each frequency Compute sound power for the system Add power for all modes Make design changes Panel acoustic contribution analysis Sensitivity analysis Iterate until desired solution is obtained Perform the final analysis using standard methodology e.g. BEM, Test

    21. Allows the study of design variations rapidly Vibrational characteristics determined using FEA, Test, NAH, etc. Acoustic characteristics computed using enhanced Rayleigh Method Definition of a single parameter permits objective comparison of designs Summary

    23. Concern Duct system Source Termination Path between source and termination Acoustic performance depends on source-path interaction Insertion Loss Difference between SPL at reference point with and without path element (muffler) Transmission Loss

    24. Boundary Element Cutaway Exploded View of 7-Zone Muffler Muffler Model

    25. Sound Field

    26. Facilitates Sub-system modeling Computes important acoustical quantities Sound pressure Sound intensity Sound power Transmission loss Effect of mean-flow is easily incorporated Summary

    28. CAT/COMET Interface Bringing tools to product development process Completely integrated process Designer should not have to leave familiar CATIA interface Use powerful mesh creation of CATIA Use all analysis capabilities of COMET

    29. Analysis Process - I Noise caused by the vibration of structure Define geometry (transmission housing) ANMESH Define vibration = Specification of surface velocities Test or FEA structural analysis ANPHYSIC+LOAD

    30. Analysis Process - II Define locations at which results (I.e. sound pressure) are desired Single point or group of points ANMESH Define material properties of acoustic domain Density and speed of sound ANPHYSIC+PROPERTY

    31. Analysis Process - III Set analysis parameters Frequency of analysis ANMANAGE+ANALYSIS Solve acoustic problem using COMET Display results (acoustic characteristics) Surface of the domain and/or within the domain COMET/Vision

    32. Summary Completely integrated process Available to analysts and designers Import FEA results from ELFINI, ANSYS, NASTRAN, ABAQUS, COSMOS Import test data from I-DEAS, CADA-X Use powerful mesh creation of CATIA Use all analysis capabilities of COMET Post Processing Options CATIA or COMET/Vision

    34. Tire Noise

    35. Concern Characteristics Many potential noise sources Complex interactions Difficult to model accurately Goals Identify the noise source Predict the sound field Predict influence of design changes

    36. Nearfield Acoustic Holography Forward problem Vibrating structure causes sound = Known sound source Source is not always easy to determine Inverse problem - Source identification

    37. Traditional and COMET NAH Traditional NAH Models plane sources Measurement surface is plane Reconstruction surface is mostly plane COMET NAH Models arbitrary 3D sources Arbitrary measurement surface Reconstruction on arbitrary 3D surface

    38. Acoustic Pressure at Measurement Surface Sound pressure at measurement surface Location and number of microphones depend on the frequency NAH identifies the source

    39. Source Identification

    40. Environmental Modification

    41. Next Generation NAH Presently applied to exterior problems NAH for interior acoustic at AAC is funded by NASA Develop NAH for source identification inside aircraft Verification using NRL experimental data inside aircraft Next generation of COMET NAH extends the source identification capability to interior noise analysis

    42. Summary Allows flexible measurement layout plane, three-dimensional Allows source identification in complex three-dimensional geometry Allows mixed measurement data pressure as well as velocity Reconstruction at measurement surface is easily verified Effect of design modification is easily studied

    44. Easy-to-Use Interface “Written by users for users” Icons call management panels Logical step by step process Easy to learn and operate ANSYS, ABAQUS, Hypermesh, I-DEAS, CADA-X, COSMOS, NASTRAN and PATRAN datafiles translated

    45. COMET Service & Support AAC’s goal is to support solving acoustic problems, not simply software like some competitors Responsive and practical technical support for real solutions to your problems Years of experience in automotive, aerospace, heavy equipment, etc...

    46. COMET Evolution - I 1994 Version 1.0 Basic (Uncoupled) BEA Module Advanced (Coupled) BEA Module Acoustic FEA Module Vision (GUI) Module Version 2.0 Spherical and plane wave sources Version 2.1 Restart capability, Structural damping 1995 Version 2.2 Direct out-of-core solver, Sensitivity analysis, Panel contribution analysis Version 3.0 Frequency matrix interpolation, Acoustic holography, (CHIEF) - overdetermined system analysis, unique exterior solution for direct

    47. COMET Evolution - II 1996 Version 3.1 Iterative solver, Discontinuous impedance, Reverberant analysis, Test data correlation 1997 Version 3.2 Windows NT Version UNIQUE - interior solution for indirect 1998 Version 4.0 SAFE Module Mean flow, Indirect out-of-core solver, Rayleigh Integral, Transient Analysis, CAT/COMET Module

    48. COMET Modules Basic Acoustic Boundary Element Analysis Advanced Acoustic Boundary Element Analysis Acoustic Finite Element Analysis SAFE - Structural Acoustic Foam Engineering (New) SAOpt - Structural Acoustic Optimization (1999) COMET Integration with CATIA - Separate Module (New) COMET/Vision

    49. COMET Advantages SAFE superior in capabilities to any other package Nearfield Acoustics Holography capabilities not available anywhere else All software written by AAC Consistent interface Fully supported No need to load or reload modules Written by users for users Thoroughly tested in engineering service before release

    50. Partial Customer List 3M Corporation Bell Helicopter Boeing Denso Donaldson Company DuPont Ford Motor Company Harman-Motive, Inc. Hyundai Motors Ibaraki NEC Company, Ltd Isuzu Motors, Ltd. Komatsu, Ltd. Lear Corporation Lockheed Martin Meritor Automotive NASA Nippon Sharyo, Ltd. Onan Corporation Prince/JCI Raytheon Aircraft Company Rieter Automotive Roush Anatrol, Inc. Samsung Advanced Industrial Technology Siemens Sound Alliance Thona Vickers, Inc.

    52. Partners and Affiliations Over $2 Million in Funding from NASA Leading U.S. developer of acoustic software Dassault partner for acoustics integration with CATIA University Affiliations Purdue University, California Institute of Technology, Iowa State University, Georgia Institute of Technology, University of Michigan

    54. Automated Analysis Corporation Regional offices near major business centers: Detroit, Chicago & London Experience and customers in automotive, aerospace and industrial markets (about half in automotive) ISO 9002 Registration Long-standing and PREFERRED supplier to major corporations such as Chrysler, Ford, General Motors, and Caterpillar

    55. COMET Offers the Solutions You Need Provides tools for practical acoustics Offers state-of-the-art Solution Methods Models complex and large applications Generates fast and accurate solutions User friendly - You don’t need to spend hours learning the software Best support in the industry - We solve acoustic problems Available through purchase or lease

    56. Sound Field

    57. Worldwide Distributors Australia LEAP Ltd. Benelux FEM-Consult Denmark Unicus Eng. France ADDL Germany CAD-FEM

    58. CAT/COMET Interface Bringing tools to product development process Completely integrated process Designer should not have to leave familiar CATIA interface Use powerful mesh creation of CATIA Use all analysis capabilities of COMET